<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>

  <body>
    <div id="app">
      <div>
        <p>请选择你要购买的书籍</p>
        <ul>
          <li v-for="(item,index) in arr" :key="item.id">
            {{item.name}}
            <button @click="item.count++">买书</button>
          </li>
        </ul>
        <table border="1" width="500" cellspacing="0">
          <tr>
            <th>序号</th>
            <th>书名</th>
            <th>单价</th>
            <th>数量</th>
            <th>合计</th>
          </tr>
          <tr v-for="(item,index) in arr" :key="item.id">
            <th>{{index+1}}</th>
            <th>{{item.name}}</th>
            <th>{{item.price}}</th>
            <th>{{item.count}}</th>
            <th>{{item.price * item.count}}</th>
          </tr>
        </table>
        <p>总价格为:{{totalPrice}}</p>
      </div>
    </div>
    <script src="../vue.js"></script>
    <script>
      const app = new Vue({
        el: '#app',
        data: {
          arr: [
            {
              name: '水浒传',
              price: 107,
              count: 0
            },
            {
              name: '西游记',
              price: 192,
              count: 0
            },
            {
              name: '三国演义',
              price: 219,
              count: 0
            },
            {
              name: '红楼梦',
              price: 178,
              count: 0
            }
          ]
        },
        computed: {
          totalPrice() {
            return this.arr.reduce(
              (sum, item) => sum + item.price * item.count,
              0
            )
          }
        },
        methods: {
          add(id) {
            const res = this.arr.find(item => item.id === id)
            res.count++
          }
        }
      })
    </script>
  </body>
</html>
